This invention relates generally to suppression of accidental fires, for example those involving cooking oil or fat, and more particularly concerns employment of portable equipment and method for producing pure water mist useful in such suppression, as well as extinction of such fires.
In recent years, the development of high-efficiency cooking equipment with high energy input rates and the widespread use of vegetable oils with high burning temperature have increased potential risks to life and property loss. Almost 50% of all accidental fires in hotels, restaurants and fast food outlets start in kitchens and the majority of these involve liquid cooking oil or fat fires. These fires are the hardest to extinguish and are easily re-ignited. Suppressing cooking oil fires has been identified as the primary fire challenge in restaurant cooking areas. Recently cooking oil fires, due to their different behavior from other types of liquid fuel fires, were re-classified into a new class of fire, Class K, by the National Fire Protection Association (NFPA); a similar classification is also being considered by the Loss Prevention Council and other agencies around the world.
Previous studies showed that foam, powder and carbon dioxide are not as effective in suppressing cooking oil fires as they are for other types of liquid fuel fires. Currently, wet chemical agents, as defined by NFPA-17A, are the primary means used to extinguish grease fires in cooking areas. They are effective in extinguishing these fires, but may cause irritation to the skin and eyes as well as clean-up problems after fire extinguishment. Furthermore, the system cost of wet chemical agents is relatively high. As a result, there is a significant need or improving fire safety and for reducing the cost of protecting restaurant cooking areas through the introduction of a portable extinguishing system or systems.
It is a major object of the invention to provide method and apparatus to efficiently and effectively suppress such fires, through use of portable apparatus to produce water mist. Such mists are non-toxic, and do not contribute to environmental problems.
Basically, the invention provides a method of extinguishing a fire characterized by production of flames openly rising above an upwardly presented liquid fat or grease zone, the fat or grease being combustible to produce the fire. The steps of the method include
a) providing a container containing pressurized aqueous liquid,
b) providing a valve controlled outlet from said container, there being a valve controlling handle,
c) providing an elongated flexible tube having an inlet end to receive said pressurized liquid, and having an outlet end,
d) providing an elongated relatively stiff metallic tube having an inlet end in communication with the flexible tube outlet end, said metallic tube having an angled outlet end portion that extends at an angle a relative to a length direction,of the metallic tube, where
xcex1 greater than 50xc2x0,
e) providing a mist producing nozzle at said outlet end portion,
f) and releasing pressurized liquid from the bottle and tubes, by operation of said handle, and via said nozzle to produce said mist while manipulating said elongated tube to cause mist discharge downwardly toward said flaming liquid fuel bath.
An added object is to provide portable apparatus for quicker movement to a fire location, and that includes:
a) a portable container and a pressurized aqueous liquid therein,
b) an elongated flexible tube having an inlet end to receive pressurized liquid from the container, and having an outlet end,
c) an elongated relatively stiff metallic duct having an inlet in communication with the flexible tube outlet end, said duct having an angled outlet end portion that extends at an angle xcex1 relative to a length direction of said duct, where
xcex1 greater than 50xc2x0,
d) and a mist producing nozzle located at the outlet end of the duct, whereby liquid flows via a pressure releasing valve from the container, the duct and nozzle, as mist, while the duct is manipulated to cause said duct end portion to extend at said angle xcex1, for encompassing the flames with mist.
Another object includes the step of providing the metallic tube to be of a length to enable grasping of the tube at a location closer to the flexible tube then to said angled end portion of the metallic tube. As will be seen, manipulation of the tube is effected to cause its angled outlet end portion to extend downwardly at an angle less than 35xc2x0 relative to vertical, to ensure that the downward stream of mist expands in flowing downwardly, to quickly encompass, cool and extinguish the flames. Water is delivered from the container at a pressure such that mist droplets form, and have cross sections less than 1000 microns.
It is another object of the invention to carry out the method to effect rapid conversion of such mist to steam, which expands outwardly about the fat or grease zone, and rapidly blankets or hovers closely about that zone, blocking air or oxygen access to the fat or grease zone.
Rapid mist stream formation and travel into the flames is effected by supply of pure water to the nozzle at a pressure level between 150 and 250 psi, and preferably above 175 psi. Also, the length of time needed for mist stream delivery toward the fat or grease zone is typically less than about 15 seconds, for effecting flame extinction. The use of mist instead of water droplets assures such rapid flame extinction, since mist provides maximum water surface area exposed to the flame, with wide area distribution.
A yet further object is to provide portable fire fighting apparatus that meets multiple xe2x80x9cKxe2x80x9d rating requirements, as follows:
A) protects against flames resulting from combustion of paper, wood, cloth and plastic materials
B) protects against flames produced by combustible liquids, such as fats.
C) Is electrically non-conductive
D) Is useful to put out fires produced in commercial kitchens.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: